If two black holes collide unobserved, do they make a sound? A black hole collision is more powerful than any event since the Big Bang. But when black holes collide, they do so unilluminated — emanating only gravitational waves; the only evidence would be the sound of spacetime ringing. Janna Levin, Barnard College Professor of Physics & Astronomy, shares the aspirations and the trials of the scientists who embarked on a 50-year-long endeavor to capture these elusive gravitational waves — allowing us to record the soundtrack of the universe.